Recently, networking and multi-function of various devices used in a production site are improved with the progress of Information and Communication Technology (ICT). Specifically, there has been put into practical use a system in which a control device such as a programmable logic controller (PLC), an input/output (I/O) device such as a sensor and a relay, and an actuator such as an inverter and a motor driver are connected and integrated through a network.
Various log output functions are mounted on the control system such that a malfunction generated during a system configuration or a system running can be investigated ex post facto. For example, Japanese Patent Unexamined Application No. 2015-176370 discloses a control system that can easily recognize a state of the control device during generation of a factor of an event.
In the networking and multi-functionalized control system, the network itself and the device and unit connected to the network are correlated with each other, and in the case that some abnormal factor is generated, a large amount of logs caused by the factor are output in some cases. There is a demand for easily specifying the factor generated from the large amount of logs.